Electric oven



AMarch-30 1926. 1,578,662

v l F. L. HUNTER v ELECTRIC OVEN Filed Nov.

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Patented 'Maxx 30, 1926i.

UNITED STATES PATENT rFicE.

FREDERICK L..H`UNTER, OF EAST ORANGE, NEVJ JERSEY, ASSIGNOR TO TVESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW Yogur.

ELECTRIC OVEN.

Application filed November 19, 1921. Serial No. 516,308.

To all whom t may concern.'

Be it known that I, FREDERICK L. HUNTER, a citizen of the United States, residing at Eastv Orange, inthe county of Essex, State of New Jersey, have invented certain new and useful Improvements in Electric Ovens, of which the following is a full, clear, concise, and exact description.

Thisinvention relates to the exhaustion of vacuum vessels and pertains more especially to an oven for heating v-acuum tubes during the pumping thereof.

The object of this invention is a simpl andinexpensive oven capable of quickly and efficiently heating the electrodes of a vacuum tubev during .the exhaust thereof.

Ovens heretofore used for heating vacuum tubes during exhaustion have comprised.

casings lined with heat insulating material. The heat capacity of these ovens is quite large, and inorder to bring them up tothe desired temperature without a considerable waste of time it was necessary to make the initial power input of considerably greater value than was needed to maintain the oven at the desired temperature. Then after the desired temperature `had been obtained it was necessary to reduce the power input to that needed tol maintain the ovens at the desired temperature. It has also been nec.- essary when using these ovens to heat vacuum tubes to be exhausted for a considerable time with the interior ofthe tubes in communication with the atmosphere, inV order to allow the electrodes to be raised to the desired temperature by heat transmitted from the heating element to t-he wall of the tube and from the wall of the'tube to the electrodes by convection.

This `invention provides a low heat capacity oven casing, the interior ofwhich'is a good reflector of heat, and a pair ofheating elements arranged a short distance from the side walls of the oven. Because of the low heat capacity of the oven, only a slight amount of the initial power input is absorbed by the oven and the remainder of the power input quickly heats up the oven to the temperature at which the heat radiated from the' exterior of the oven equals the power input. It is unnecessary to regulate the power input until it is desired to shut olf the oven. The heat radiated from the heating elements directly toward the vacuum tube together with that radiated toward it by reflection from the walls is sulfici'ent to heat the electrodes almost immediately to the desired temperature. As radiated heat passes through a vacuum as easilyv as through the atmosphere, the above described arrangement allows the exhaustion of the tubes'to be begun simultaneously with the starting ofthe oven and, therefore, greatly' reduces the time spent in the pumping operation.

The invention further insures that the tubes are entirely free of all moisture when they are sealed oit. This is accomplished by enclosing the vheader to which the tubulaturesof the vacuum tubes are attached within the top wall of the oven. Thus, the moisture removed from the tubes is driven beyond the header and there is no possibility of any moisture beingretained within the tubes. i Y Other objects and advantages of the'invention will be apparent from the following specification and accompanying drawing wherein Fig. 1 is a side elevation of the oven in its open condition and Fig. 2 isa transvverse vertical section of the oven when closed.

The oven comprises a lower box-like portion 10 and a substantially semi-cylindrical cover 11. The longitudinal upper edges of. the box 10 are offset vto allow the cover to iitrwithin the top of the box. The box 10` is supported by meansof standards 12 and the cover by means of the standard 13. The box 10 is adjustable up and down on the standards' 12 and is held in any desired positionI by the set screws 14.' The header 15 of the pumping al paratus is arranged within and supported y the cover 11. 'Depending from each end of the cover 11 is a strap 16. The straps 16 are connected at their-flower ends by a strip 17 of insulating material in which are provided apertures forthe lead wires of the tube to be exhausted. The bottomV wall of the oven'is longitudinally slotted alonfg` the center line in order to allow the lead wires of the tubes being exhausted to extend out of the casing. This slot is normally closed by the strip 17. The tubes to be exhausted are suspended from the header 15 by their tubulatures and are arranged along the longitudinal center of the casing. Arranged in the box 10,

isam'aderof a; metallic: ribbon, the; edgesofii which.. are;Y directedv toward4 the. tubes.- to:be-

evacuated and toward one side Wall of the casing. The casing 1s free of heat obstruct ing or heat absorbing material.

oforV lined Ywith a material which is aigood like.; The Walls ofthe box andcover are 1x5 quiteith'in andof low heat capacity. The

small?" heat capacity of the casing allowspractically vall lofthe initial 'power input to' beutilized, in heatingthe interior of'the. ovenA so that it` isf quickly raised to the desiredftemperature Without increasing the power inputbeyond that necessary to main:-

tain theyoven at the proper temperature... It

isihuspossible to puta definite amount ofY powerinto the oven which -Will quickly heat itf-tofandmaintain it atVv the desired temperature Without regulation. p

The heat.Wavesradiatedfrom the resistanceelement directlyftowardlthe tube and thoserreiected toward. the tube from the inner4 surfaces-ofthe casing serve to heat the electrodes to the temperature necessary to drive offthe absorbed gases. As heat Waves are effectively `transmitted lthrough the mediu-mof thefether of'an evacuated space, the heat needfnotbe applied A'until the evacuation of..`the tubeisstartedoris partially vcom-v pileted. The design ofthe cover=llfis such that the Waves radiatedfrom the iatsurface. ofthe resistance ribbon are reflected toward-the tubes. The arrangement ofthe headerfl Within Ithe topy Wall'. o-f the oven insures that? all moisture Within the tubes Will befdriven sufciently far intoL the pumpgingiapparatus thatthere Will be no danger of,` any moisture being left in'- the tube after evacuation;

It is obvious that otherl means: may be used for supplying/.energythrough the ether in theevacuatedbulb for heatingrthe elec-ctrodes gvvithout departinginr any Wise from thefspirit ofthe invention as set` forth in the :appended claims.

That is claimed is:

1.",.An velectric oven comprising a casing substantially free ofheat absorbing ,mate rial, saidcasingbeing, composed of heat reflecti1igmaterial, .and a source of heat" arranged'within said casing but spaced-from the :Wall thereof.

'Ql'An electrim oven comprising a casing substantiallyr free of heat absorbing material and havingiaheat reflecting surface, .and a gridflillrecsource of lheat varranged Within said .casingbut 'spaced from the Wall thereof.

3. An electric oven comprising a casing, a

The box l0 and the cover1l'are`form'ed rvaeea cover for said casing, said cover being adaptedl to. receive thefheader" of an" evacuating device, anda source Ofheat arranged' Within'Y saidv casing but spaced from the Wall thereof.

la Anf electric oven comprising; a1. casing, a substantially semi-cylindrical: cover# for saidcasing, said cover being adaptedto receive the header of an evacuating device, and a' source of''heat 'arranged Within said casing.

5. An electric oven comprising a casing.t a cover.. for saidl casing; said' casing being* movablezrelative to said: coveig means Withinthe' cover to `support a yvacuumv tubelto'be'.`

exhausted', and a source ofheatwithin' said casing..

6; -An electric oven compris-ingai casing" having a slot', a cover'for said casir'rg'mov'-` able relative to saidcasing, mea-nsvvitlfiir the cover tosupport` a vacuumtube' to --be erhfaustech a source offheat'vvithlnA saidcas# close said slot.

7.' Anfelectric oven comprising a casing composed i of av single laye-r of sheet" metal whereby the. heatcapacity of; said'lovenis" low, the inner Wall of saidcasinfgprese-nting a heatreilectmgsurface, anda-source 'of 'heat arranged Within said? casing' but spaced from thewallthereof.

8; An electric oven'comprising:acasing5 a. cover.- forl said casing adapted l toreceive the header of an evacuatmgv device," said' cover and casing being oflow heat capacity and havingV a heat reflecting interior'surface;

and a sourceiofheat arrangedfvvi'thin said casing:

9.l An. electric ovencomprising-acasing5 a' cover for `said casing',Y saidl cover fand'caslng beingY ofi low heat capacity and having* a heat reflecting interior' surface,` means for' supportingsaid cover' and casingin movablerelation toeach' other, meanswithin the cover to'supp'ort a vacuunr'ttrbe to be eiausted, and a'source of heatWithi-nsaid casing.

l0; An .electric oven comprising 'a' casing: aV cove-rV for'said` casing, said casingand' cover being oflow heat capacity and-hrwL7 ing a heat reflecting interior surface," and means iforysupporting said cover' and :casing in shiftable relation.

1l."v An electric oven comprising'a casing havingfa'slot, .a cover for saidicasingj sai-d casing being movable relative to said cover; said cover and casinggbeing oflow heat caf placity and having a heat-reflecting interior surface7 means Within' theV coverttofsupport avacuum tube to beexhausted," awsource of heat Within` said casing, andv` means' su-pgf ported by said' cover to closey said slot.

l2." An electric; ovenA comprisingfar casing' of .low heat capacity composedl of f' a single ing interior surface,.and la heatingl unitar-v ranged adjacent to but spaced from said surface.

13. An electric oven comprising a low heat capacity casing composed of a single layer of sheet metal having a heat reflecting interior surface, a frame arranged substantially parallel to a Wall of said easing but spaced from the Wall thereof, and a heating unit supported by said frame.

14. An electric oven comprising a 10W heat capacity casing' composed of a single layer of sheet metal having a heat reflectinginner surface, and a source of heat arranged Within said casinghut spaced from the Wall thereof.

In Witness whereof, I hereunto subscribe my name this 10th day of November A. D., 1921.

FREDERICK L. HUNT ER. 

